Two major problems associated with wool are its tactile discomfort (itchiness) and tendency to shrink. Improvements in softness and handle of wool can be achieved by addition of various chemical agents such as silicone softeners or by addition of proteolytic enzymes. The cost of these improvements may be greater than the moderate benefits achieved. Changes in one property of wool can affect other properties, sometimes adversely. For example, protease treatments normally have adverse effects on strength and weight of wool material.
Methods to generate shrink-resistant wool are known. The most commonly used method is the IWS/CSIRO Chlorine Hercosett process, which comprises an acid chlorination of wool, followed by a polymer application. This process imparts a high degree of shrink-resistance to wool, but adversely affects the handle of wool, and generates environmentally damaging waste.
Methods to reduce shrinkage of wool which do not result in release of damaging substances to the environment have been suggested, including enzymatic processes as well as benign chemical processes such as low-temperature plasma treatments. Plasma treatment is a dry process which involves treating wool fiber material with electrical gas discharges (so-called plasma). At present, there are obstacles (cost, capacity, compatibility) to large-scale commercialization of a plasma treatment process.
Various enzymatic methods have been used to treat wool. JP-A 51099196 describes a process to treat wool fabrics with alkaline proteases. JP-A 3213574 describes a method to treat wool using transglutaminase (an enzyme naturally found in wool follicles from sheep) or a solution containing transglutaminase. WO 98/27264 describes a method for reducing the shrinkage of wool comprising contacting wool with an oxidase or a peroxidase solution under conditions suitable for reacting the enzyme with wool. U.S. Pat. No. 5,529,928 describes a process for obtaining a wool with a soft woolly handle and shrink-resistant properties by using an initial chemical oxidative step or an enzyme treatment (e.g. a peroxidase, a catalase, or a lipase) followed by a protease treatment, followed by heat treatment. EP 358386 A2 describes a method to treat wool which comprises a proteolytic treatment and one of or both an oxidative treatment (such as NaOCl) and a polymer treatment. EP 134267 describes a method for treating animal fibers with an oxidizing agent, followed by a proteolytic enzyme in a salt-containing composition.
The environmental and performance deficiencies associated with current industrial processes for wool treatment substantiate the need for novel processes that provide further improvements relating to shrink-resistance or softness. Enzymatic methods for treating wool, used alone or in conjunction with an oxidative chemical step, have had little commercial value, a fact that is attributable to their relatively high costs and their tendency to damage wool by causing weight and strength losses. There is a need for an improved enzymatic method to treat wool, wool fibers, or animal hair material which imparts improvements in softness, shrink-resistance, appearance, whiteness, dye uptake, and resistance to pilling, but causes less fiber damage than known enzymatic treatments.